Benefits of sward diversity for agricultural grasslands.

A pan-European experiment carried out at 28 sites across Europe showed strong benefits of sward diversity inagricultural grasslands. We systematically varied the relative abundance of four agronomic plant species (sown speciesevenness), and found that 4-species mixtures yielded more forage than could be expected on the basis of the monocultureyields. Mixtures generally yielded more than even the best performing monoculture (transgressive overyielding). Mixturesstrongly reduced the incidence of unsown species in the sward. These diversity effects were consistent over the wide rangeof environmental conditions and persisted over three harvest years and in highly fertilized conditions. These results indicatea strong potential for agronomic mixtures to contribute to more sustainable agricultural systems. Agronomic diversity canimprove forage yield and reduce weed invasion in intensively managed grasslands, and may also enhance the provision ofother ecosystem services.